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Tuesday, November 13, 2018

It has been
hypothesized that your genetic makeup can predict which weight loss strategy will
be the most effective for you. In this interesting study, 609 adults were
randomized to either a low-fat or low-carb diet for 12 months. Previous
research has suggested that a certain genotype that impacts carbohydrate
metabolism may help a person be more successful with a low-carb diet. Similarly,
another genotype that influences fat metabolism has been identified that may
make a person more successful on a low-fat diet. Before the trial began,
subjects were tested for this low-fat or low-carb response gene sequence.

Among the
participants randomized to the low-fat diet, 130 had the low-fat gene and 83
had the low-carb gene. Among the participants randomized to the low-carb diet,
114 had the low-fat gene and 97 had the low-carb gene. By the end of the 12
month follow-up, there were no differences in weight lost between the two
groups and neither the low-fat or low-carb genotype predicted weight loss
success.

Journal of the American Medical Association
2018; 319:667.

Take Home Message

Although the idea
that our genes can tell us what weight loss diet is best for us is intriguing,
this study does not provide evidence that this is the case. More research is
needed before we can definitively answer this question.

In this investigation, Harvard
researchers created a dietary scoring system of foods that promote a high
insulin response. They called it the Empirical Dietary Index for
Hyperinsulinemia (EDIH). This is different than the glycemic index, which
focuses on the blood sugar effects of carbohydrate containing foods. This index
includes all foods that spike insulin after consumption.

The food groups that
contributed to a low EDIH score included wine, coffee, fruit, high fat dairy
products and green leafy vegetables.

Over 120,000 men and women from
the Nurses’ Health Study and the Health Professional Follow-up Study had an
EDIH score calculated for their diet and were followed for 26 years. Subjects
with the greatest EDIH score had a statistically significant 26% higher risk of
colon cancer when compared to subjects with the lowest EDIH score. American Journal of Clinical Nutrition 2018; 108:363-70.

Take Home Message

When choosing a diet to promote weight loss, you always
want to look at the long-term health effects of the diet as well.

The EDIH score takes the idea of the glycemic index a
step further. The GI focuses on the blood sugar effects of carbohydrate foods. The
EDIH score includes any food that increases insulin. A lot of these foods are
proteins. Many popular current diets are really high in animal protein, and
this study makes you think twice about them.

As far as mechanisms go, it is thought that very high
levels of insulin, and insulin derived growth hormone may be carcinogenic.

In addition to keeping your glycemic index low, it is a
good idea to go easy on the animal proteins. It is particularly important to
limit red meat and processed meats. It is also a good idea to substitute
vegetable proteins such as beans, nuts, whole grains and legumes for animal
proteins whenever possible.

Carbohydrate
consumption has been a hot button issue in the field of nutrition for decades.
The type and amount of carbohydrate we should be including in our diets is the
subject of intense debate in both the research and weight loss communities.
This is a subject that is near and dear to my own heart since carbohydrate
metabolism was the subject of my own doctoral research. A new study has been
published on this topic that is well done and very important.

The Article

This investigation
actually consists of two separate studies (Reference 1). The first is a
prospective cohort study using the ARIC cohort (The Atherosclerosis Risk in
Communities). The second is a meta-analysis including 7 separate studies.

Results

Prospective
Cohort Study in the ARIC Cohort

Over 15,000 adults
aged 45-64 years in 4 U.S. communities had their diet assessed by means of a
food frequency questionnaire and were followed for 25 years. Subjects who
consumed 50-55% of their calories as carbohydrate had the lowest mortality
rate. Subjects who ate more or less carbohydrate had an increased mortality
risk.

-A 50 year old
subject consuming less than 30% of calories as carbohydrate would have a
projected life expectancy of 29.1 years.

- A 50 year old subject
consuming 50-55% of calories as carbohydrate would have a projected life
expectancy of 33.1 years.

A 50 year old
subject consuming greater than 65% of calories as carbohydrate would have a projected
life expectancy of 32 years.

Meta-analysis

The meta-analysis
consisted of 8 separate studies with a total of 432,179 subjects and showed a
similar result. There was an increased risk of mortality with both a low and
high carbohydrate intake when compared to a moderate carbohydrate intake.

Subjects consuming
less than 40% of calories as carbohydrate had a statistically significant 20%
higher risk of mortality.

Subjects consuming
greater than 70% of calories as carbohydrate had a statistically significant
23% higher risk of mortality.

Substituting
animal fat and protein for carbohydrate resulted in an increased risk of
mortality.

Substituting
vegetable fat and protein for carbohydrate resulted in a decreased risk of
mortality.

Conclusions And Recommendations

Many people
manipulate their carbohydrate consumption in an effort to lose weight. It is
really important to examine what effect these weight loss diets may have on
long term health. My professional goal has always been to provide a strategy
that helps my client lose weight effectively, while improving overall health
and decreasing risk of chronic disease.

This study sheds
some light on the long-term health effects of diets that severely manipulate carbohydrate
consumption. The mechanisms are pretty straight forward. A low carb diet will
generally include less healthy foods such as fruits, vegetables and whole
grains and higher amounts of red meat and saturated fat. This results in fewer
vitamins, minerals, fiber and cancer fighting phytochemicals. This eating
pattern likely results in higher levels of oxidative stress, inflammation and
biological aging.

On the other hand,
diets very high in carbohydrates tend to include too many refined carbohydrates
and not enough healthy vegetable fat. This results in a much higher dietary
glycemic load, which has been associated with many negative health outcomes.

Here is what we
learn from this important study:

1) Going very low
carb is probably not a great idea.

2) Going very high
carb is probably not a great idea.

3) Stay in the mid
carb range, which is around 50-55% of calories.

4) The quality of
carbohydrates consumed is of the utmost importance. Focus on low glycemic carbs
such as fruits, vegetables, legumes and whole grains.

5) The majority of
your fat should be vegetable fats such as nuts, avocado, nut butters, seeds and
healthy vegetable oils such as olive oil and canola oil.